Optically pure (R)-1-bromo-1-phenylethane is stirred in aqueous acetone, where the reaction proceeds by $S_{N} 1$ through ion pairs. The 1-phenylethanol formed is

Anearly racemic, with a slight excess of the (R) enantiomer
Bpure (R) enantiomer
Cnearly racemic, with a slight excess of the (S) enantiomer
Dpure (S) enantiomer

Answer: C

The planar benzylic cation is attacked from both faces, so the product is nearly racemic. The leaving bromide partly shields the front face, so a little more attack occurs from the back, giving a slight excess of the inverted product. For both bromide and alcohol the priorities are

Br

OH > C X_{6} H X_{5} > CH X_{3} > H

, so inversion gives (S).

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Optically pure (R)-1-bromo-1-phenylethane is stirred in aqueous acetone, where the reaction proceeds by SN​1 through ion pairs. The 1-phenylethanol formed is

Answer: C

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Optically pure (R)-1-bromo-1-phenylethane is stirred in aqueous acetone, where the reaction proceeds by $S_{N} 1$ through ion pairs. The 1-phenylethanol formed is